We are studying the regulation of catecholamine synthesis and secretion. In particular, we are interested in the roles of cyclic adenosine 3':5' -monophosphate (cyclic AMP) and of Ca2 ion in the regulation of these processes. We plan to study these processes in pheochromocytoma cells and in normal chromaffin cells. These cells will be incubated in vitro under conditions that affect their content of cyclic AMP or their uptake of Ca2 ion, and the effects of these treatments on catecholamine secretion and on the activity of tyrosine 3-monooxygenase will be determined. We will measure tyrosine 3-monooxygenase activity by measuring the rate of dopa production by cells that are incubated with tyrosine in the presence of an inhibitor of aromatic L-amino acid decarboxylase. Dopa production and the release of endogeneous catecholamines will be measured by high-pressure liquid chromatography with electrochemical detection. We will also determine the effects of these treatments on the activity of protein kinases, and on the pattern of protein phosphorylation in these cells. The goal of these studies will be to determine the mechanisms by which cyclic AMP and Ca2 ion regulate the activity of tyrosine 3-monooxygenase. Finally, we will investigate the extent to which catecholamine secretion and catecholamine synthesis are co-ordinately regulated.